1. Field
The present specification generally relates to methods and apparatuses for fabricating glass ribbons and, more particularly, to methods and apparatuses for guiding glass cutting and preventing crackout of the glass ribbon during cutting.
2. Technical Background
Glass ribbons may be formed by processes such as the fusion draw process, the slot draw process, or other similar downdraw processes. The fusion draw process yields glass ribbons which have surfaces with superior flatness and smoothness when compared to glass ribbons produced by other methods. Individual glass sheets sectioned from glass ribbons formed by the fusion draw process can be used in a variety of devices including flat panel displays, touch sensors, photovoltaic devices, and other electronic applications.
Glass ribbons formed by the fusion draw process have beads at the edges of the glass ribbon. The beads tend to be thicker than a center portion of the glass ribbon and, thus, cool more slowly and unevenly than other portions of the glass ribbon, which causes residual stresses to develop in the glass that can lead to cracking. Particularly, when horizontally separating glass sheets from the glass ribbon at the bottom of the draw, cracks may occur inside the bead regions and propagate vertically up the draw toward the fusion draw machine. This cracking can lead to breakage and crackout, which causes loss of process time and, possibly, product. Crackout is particularly prevalent in laminate fusion processes where double bead features and complex residual stresses can exacerbate the stresses that lead to cracking upon horizontal separation of a glass sheet from the ribbon.
Accordingly, alternative methods and apparatuses for preventing crackout during horizontal separation of a glass sheet from the ribbon are disclosed herein.